Method and device for reflow soldering with volume flow control

Abstract

According to one aspect of the invention it is possible to rapidly heat a soldering item by reducing an initially larger volume flow at a constant or increasing temperature, effectively preventing small components from overheating. By using the volume flow of a convection heater to control effective heat transmission occurring on said soldering item, it is also possible to adapt the soldering process in an extremely flexible manner to special process requirements by virtue of the fact that adjustment of a modified volume flow can be controlled in a very quick and precise manner.

1. A method of soldering an item to be soldered in a transit oven comprising:
 heating the item to be soldered in a preheating zone using a preheating device to a first temperature below the melting temperature of a solder in contact with the item to be soldered; 
 subjecting the item to be soldered in a soldering zone with a first volume flow of a fluid with a second temperature higher than a melting temperature of the solder generated by a convection heater; 
 after subjecting the item to be soldered with the first volume flow, subjecting the item to be soldered in the soldering zone with a second volume flow of a fluid with the second temperature, and 
 cooling the item to be soldered below the melting temperature, 
 wherein the first volume flow is larger than the second volume flow, and 
 wherein the convection heater heats the item to be soldered from both sides with the first and second volume flows at the second temperature. 
 
   
   
     2. The method according to  claim 1 , wherein the soldering zone comprises a first section for providing the first volume flow and a second section for providing the second volume flow. 
   
   
     3. The method according to  claim 1 , wherein at least one of the first and second volume flows is statically reduced. 
   
   
     4. The method according to  claim 2 , wherein part of the first volume flow is branched off before entering the soldering zone in order to produce the second volume flow from the remaining portion of the first volume flow. 
   
   
     5. The method according to  claim 4 , wherein the branched off part of the first volume flow is used for preheating a further item to be soldered. 
   
   
     6. The method according to  claim 1 , further comprising:
 setting a maximum temperature of the item to be soldered; and 
 adjusting the second temperature of the second volume flow to substantially the set maximum temperature. 
 
   
   
     7. The method according to  claim 6 , wherein the second temperature is set to the maximum temperature. 
   
   
     8. The method according to  claim 2 , wherein at least a first convection heating unit of the convection heater is provided in a first soldering zone and at least a second convection heating unit of the convection heater is provided in a second soldering zone. 
   
   
     9. The method according to  claim 1 , wherein the first volume flow is reduced based on a measurement of the item to be soldered.